--- /dev/null
+/*
+** $Id: lgc.c,v 2.140.1.2 2013/04/26 18:22:05 roberto Exp $
+** Garbage Collector
+** See Copyright Notice in lua.h
+*/
+
+#include <string.h>
+
+#define lgc_c
+#define LUA_CORE
+
+#include "lua.h"
+
+#include "ldebug.h"
+#include "ldo.h"
+#include "lfunc.h"
+#include "lgc.h"
+#include "lmem.h"
+#include "lobject.h"
+#include "lstate.h"
+#include "lstring.h"
+#include "ltable.h"
+#include "ltm.h"
+
+
+
+/*
+** cost of sweeping one element (the size of a small object divided
+** by some adjust for the sweep speed)
+*/
+#define GCSWEEPCOST ((sizeof(TString) + 4) / 4)
+
+/* maximum number of elements to sweep in each single step */
+#define GCSWEEPMAX (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4))
+
+/* maximum number of finalizers to call in each GC step */
+#define GCFINALIZENUM 4
+
+
+/*
+** macro to adjust 'stepmul': 'stepmul' is actually used like
+** 'stepmul / STEPMULADJ' (value chosen by tests)
+*/
+#define STEPMULADJ 200
+
+
+/*
+** macro to adjust 'pause': 'pause' is actually used like
+** 'pause / PAUSEADJ' (value chosen by tests)
+*/
+#define PAUSEADJ 100
+
+
+/*
+** 'makewhite' erases all color bits plus the old bit and then
+** sets only the current white bit
+*/
+#define maskcolors (~(bit2mask(BLACKBIT, OLDBIT) | WHITEBITS))
+#define makewhite(g,x) \
+ (gch(x)->marked = cast_byte((gch(x)->marked & maskcolors) | luaC_white(g)))
+
+#define white2gray(x) resetbits(gch(x)->marked, WHITEBITS)
+#define black2gray(x) resetbit(gch(x)->marked, BLACKBIT)
+
+
+#define isfinalized(x) testbit(gch(x)->marked, FINALIZEDBIT)
+
+#define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n)))
+
+
+#define checkconsistency(obj) \
+ lua_longassert(!iscollectable(obj) || righttt(obj))
+
+
+#define markvalue(g,o) { checkconsistency(o); \
+ if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
+
+#define markobject(g,t) { if ((t) && iswhite(obj2gco(t))) \
+ reallymarkobject(g, obj2gco(t)); }
+
+static void reallymarkobject (global_State *g, GCObject *o);
+
+
+/*
+** {======================================================
+** Generic functions
+** =======================================================
+*/
+
+
+/*
+** one after last element in a hash array
+*/
+#define gnodelast(h) gnode(h, cast(size_t, sizenode(h)))
+
+
+/*
+** link table 'h' into list pointed by 'p'
+*/
+#define linktable(h,p) ((h)->gclist = *(p), *(p) = obj2gco(h))
+
+
+/*
+** if key is not marked, mark its entry as dead (therefore removing it
+** from the table)
+*/
+static void removeentry (Node *n) {
+ lua_assert(ttisnil(gval(n)));
+ if (valiswhite(gkey(n)))
+ setdeadvalue(gkey(n)); /* unused and unmarked key; remove it */
+}
+
+
+/*
+** tells whether a key or value can be cleared from a weak
+** table. Non-collectable objects are never removed from weak
+** tables. Strings behave as `values', so are never removed too. for
+** other objects: if really collected, cannot keep them; for objects
+** being finalized, keep them in keys, but not in values
+*/
+static int iscleared (global_State *g, const TValue *o) {
+ if (!iscollectable(o)) return 0;
+ else if (ttisstring(o)) {
+ markobject(g, rawtsvalue(o)); /* strings are `values', so are never weak */
+ return 0;
+ }
+ else return iswhite(gcvalue(o));
+}
+
+
+/*
+** barrier that moves collector forward, that is, mark the white object
+** being pointed by a black object.
+*/
+void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
+ global_State *g = G(L);
+ lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
+ lua_assert(g->gcstate != GCSpause);
+ lua_assert(gch(o)->tt != LUA_TTABLE);
+ if (keepinvariantout(g)) /* must keep invariant? */
+ reallymarkobject(g, v); /* restore invariant */
+ else { /* sweep phase */
+ lua_assert(issweepphase(g));
+ makewhite(g, o); /* mark main obj. as white to avoid other barriers */
+ }
+}
+
+
+/*
+** barrier that moves collector backward, that is, mark the black object
+** pointing to a white object as gray again. (Current implementation
+** only works for tables; access to 'gclist' is not uniform across
+** different types.)
+*/
+void luaC_barrierback_ (lua_State *L, GCObject *o) {
+ global_State *g = G(L);
+ lua_assert(isblack(o) && !isdead(g, o) && gch(o)->tt == LUA_TTABLE);
+ black2gray(o); /* make object gray (again) */
+ gco2t(o)->gclist = g->grayagain;
+ g->grayagain = o;
+}
+
+
+/*
+** barrier for prototypes. When creating first closure (cache is
+** NULL), use a forward barrier; this may be the only closure of the
+** prototype (if it is a "regular" function, with a single instance)
+** and the prototype may be big, so it is better to avoid traversing
+** it again. Otherwise, use a backward barrier, to avoid marking all
+** possible instances.
+*/
+LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c) {
+ global_State *g = G(L);
+ lua_assert(isblack(obj2gco(p)));
+ if (p->cache == NULL) { /* first time? */
+ luaC_objbarrier(L, p, c);
+ }
+ else { /* use a backward barrier */
+ black2gray(obj2gco(p)); /* make prototype gray (again) */
+ p->gclist = g->grayagain;
+ g->grayagain = obj2gco(p);
+ }
+}
+
+
+/*
+** check color (and invariants) for an upvalue that was closed,
+** i.e., moved into the 'allgc' list
+*/
+void luaC_checkupvalcolor (global_State *g, UpVal *uv) {
+ GCObject *o = obj2gco(uv);
+ lua_assert(!isblack(o)); /* open upvalues are never black */
+ if (isgray(o)) {
+ if (keepinvariant(g)) {
+ resetoldbit(o); /* see MOVE OLD rule */
+ gray2black(o); /* it is being visited now */
+ markvalue(g, uv->v);
+ }
+ else {
+ lua_assert(issweepphase(g));
+ makewhite(g, o);
+ }
+ }
+}
+
+
+/*
+** create a new collectable object (with given type and size) and link
+** it to '*list'. 'offset' tells how many bytes to allocate before the
+** object itself (used only by states).
+*/
+GCObject *luaC_newobj (lua_State *L, int tt, size_t sz, GCObject **list,
+ int offset) {
+ global_State *g = G(L);
+ char *raw = cast(char *, luaM_newobject(L, novariant(tt), sz));
+ GCObject *o = obj2gco(raw + offset);
+ if (list == NULL)
+ list = &g->allgc; /* standard list for collectable objects */
+ gch(o)->marked = luaC_white(g);
+ gch(o)->tt = (lu_byte)tt;
+ gch(o)->next = *list;
+ *list = o;
+ return o;
+}
+
+/* }====================================================== */
+
+
+
+/*
+** {======================================================
+** Mark functions
+** =======================================================
+*/
+
+
+/*
+** mark an object. Userdata, strings, and closed upvalues are visited
+** and turned black here. Other objects are marked gray and added
+** to appropriate list to be visited (and turned black) later. (Open
+** upvalues are already linked in 'headuv' list.)
+*/
+static void reallymarkobject (global_State *g, GCObject *o) {
+ lu_mem size;
+ white2gray(o);
+ switch (gch(o)->tt) {
+ case LUA_TSHRSTR:
+ case LUA_TLNGSTR: {
+ size = sizestring(gco2ts(o));
+ break; /* nothing else to mark; make it black */
+ }
+ case LUA_TUSERDATA: {
+ Table *mt = gco2u(o)->metatable;
+ markobject(g, mt);
+ markobject(g, gco2u(o)->env);
+ size = sizeudata(gco2u(o));
+ break;
+ }
+ case LUA_TUPVAL: {
+ UpVal *uv = gco2uv(o);
+ markvalue(g, uv->v);
+ if (uv->v != &uv->u.value) /* open? */
+ return; /* open upvalues remain gray */
+ size = sizeof(UpVal);
+ break;
+ }
+ case LUA_TLCL: {
+ gco2lcl(o)->gclist = g->gray;
+ g->gray = o;
+ return;
+ }
+ case LUA_TCCL: {
+ gco2ccl(o)->gclist = g->gray;
+ g->gray = o;
+ return;
+ }
+ case LUA_TTABLE: {
+ linktable(gco2t(o), &g->gray);
+ return;
+ }
+ case LUA_TTHREAD: {
+ gco2th(o)->gclist = g->gray;
+ g->gray = o;
+ return;
+ }
+ case LUA_TPROTO: {
+ gco2p(o)->gclist = g->gray;
+ g->gray = o;
+ return;
+ }
+ default: lua_assert(0); return;
+ }
+ gray2black(o);
+ g->GCmemtrav += size;
+}
+
+
+/*
+** mark metamethods for basic types
+*/
+static void markmt (global_State *g) {
+ int i;
+ for (i=0; i < LUA_NUMTAGS; i++)
+ markobject(g, g->mt[i]);
+}
+
+
+/*
+** mark all objects in list of being-finalized
+*/
+static void markbeingfnz (global_State *g) {
+ GCObject *o;
+ for (o = g->tobefnz; o != NULL; o = gch(o)->next) {
+ makewhite(g, o);
+ reallymarkobject(g, o);
+ }
+}
+
+
+/*
+** mark all values stored in marked open upvalues. (See comment in
+** 'lstate.h'.)
+*/
+static void remarkupvals (global_State *g) {
+ UpVal *uv;
+ for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
+ if (isgray(obj2gco(uv)))
+ markvalue(g, uv->v);
+ }
+}
+
+
+/*
+** mark root set and reset all gray lists, to start a new
+** incremental (or full) collection
+*/
+static void restartcollection (global_State *g) {
+ g->gray = g->grayagain = NULL;
+ g->weak = g->allweak = g->ephemeron = NULL;
+ markobject(g, g->mainthread);
+ markvalue(g, &g->l_registry);
+ markmt(g);
+ markbeingfnz(g); /* mark any finalizing object left from previous cycle */
+}
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** Traverse functions
+** =======================================================
+*/
+
+static void traverseweakvalue (global_State *g, Table *h) {
+ Node *n, *limit = gnodelast(h);
+ /* if there is array part, assume it may have white values (do not
+ traverse it just to check) */
+ int hasclears = (h->sizearray > 0);
+ for (n = gnode(h, 0); n < limit; n++) {
+ checkdeadkey(n);
+ if (ttisnil(gval(n))) /* entry is empty? */
+ removeentry(n); /* remove it */
+ else {
+ lua_assert(!ttisnil(gkey(n)));
+ markvalue(g, gkey(n)); /* mark key */
+ if (!hasclears && iscleared(g, gval(n))) /* is there a white value? */
+ hasclears = 1; /* table will have to be cleared */
+ }
+ }
+ if (hasclears)
+ linktable(h, &g->weak); /* has to be cleared later */
+ else /* no white values */
+ linktable(h, &g->grayagain); /* no need to clean */
+}
+
+
+static int traverseephemeron (global_State *g, Table *h) {
+ int marked = 0; /* true if an object is marked in this traversal */
+ int hasclears = 0; /* true if table has white keys */
+ int prop = 0; /* true if table has entry "white-key -> white-value" */
+ Node *n, *limit = gnodelast(h);
+ int i;
+ /* traverse array part (numeric keys are 'strong') */
+ for (i = 0; i < h->sizearray; i++) {
+ if (valiswhite(&h->array[i])) {
+ marked = 1;
+ reallymarkobject(g, gcvalue(&h->array[i]));
+ }
+ }
+ /* traverse hash part */
+ for (n = gnode(h, 0); n < limit; n++) {
+ checkdeadkey(n);
+ if (ttisnil(gval(n))) /* entry is empty? */
+ removeentry(n); /* remove it */
+ else if (iscleared(g, gkey(n))) { /* key is not marked (yet)? */
+ hasclears = 1; /* table must be cleared */
+ if (valiswhite(gval(n))) /* value not marked yet? */
+ prop = 1; /* must propagate again */
+ }
+ else if (valiswhite(gval(n))) { /* value not marked yet? */
+ marked = 1;
+ reallymarkobject(g, gcvalue(gval(n))); /* mark it now */
+ }
+ }
+ if (prop)
+ linktable(h, &g->ephemeron); /* have to propagate again */
+ else if (hasclears) /* does table have white keys? */
+ linktable(h, &g->allweak); /* may have to clean white keys */
+ else /* no white keys */
+ linktable(h, &g->grayagain); /* no need to clean */
+ return marked;
+}
+
+
+static void traversestrongtable (global_State *g, Table *h) {
+ Node *n, *limit = gnodelast(h);
+ int i;
+ for (i = 0; i < h->sizearray; i++) /* traverse array part */
+ markvalue(g, &h->array[i]);
+ for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */
+ checkdeadkey(n);
+ if (ttisnil(gval(n))) /* entry is empty? */
+ removeentry(n); /* remove it */
+ else {
+ lua_assert(!ttisnil(gkey(n)));
+ markvalue(g, gkey(n)); /* mark key */
+ markvalue(g, gval(n)); /* mark value */
+ }
+ }
+}
+
+
+static lu_mem traversetable (global_State *g, Table *h) {
+ const char *weakkey, *weakvalue;
+ const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
+ markobject(g, h->metatable);
+ if (mode && ttisstring(mode) && /* is there a weak mode? */
+ ((weakkey = strchr(svalue(mode), 'k')),
+ (weakvalue = strchr(svalue(mode), 'v')),
+ (weakkey || weakvalue))) { /* is really weak? */
+ black2gray(obj2gco(h)); /* keep table gray */
+ if (!weakkey) /* strong keys? */
+ traverseweakvalue(g, h);
+ else if (!weakvalue) /* strong values? */
+ traverseephemeron(g, h);
+ else /* all weak */
+ linktable(h, &g->allweak); /* nothing to traverse now */
+ }
+ else /* not weak */
+ traversestrongtable(g, h);
+ return sizeof(Table) + sizeof(TValue) * h->sizearray +
+ sizeof(Node) * cast(size_t, sizenode(h));
+}
+
+
+static int traverseproto (global_State *g, Proto *f) {
+ int i;
+ if (f->cache && iswhite(obj2gco(f->cache)))
+ f->cache = NULL; /* allow cache to be collected */
+ markobject(g, f->source);
+ for (i = 0; i < f->sizek; i++) /* mark literals */
+ markvalue(g, &f->k[i]);
+ for (i = 0; i < f->sizeupvalues; i++) /* mark upvalue names */
+ markobject(g, f->upvalues[i].name);
+ for (i = 0; i < f->sizep; i++) /* mark nested protos */
+ markobject(g, f->p[i]);
+ for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */
+ markobject(g, f->locvars[i].varname);
+ return sizeof(Proto) + sizeof(Instruction) * f->sizecode +
+ sizeof(Proto *) * f->sizep +
+ sizeof(TValue) * f->sizek +
+ sizeof(int) * f->sizelineinfo +
+ sizeof(LocVar) * f->sizelocvars +
+ sizeof(Upvaldesc) * f->sizeupvalues;
+}
+
+
+static lu_mem traverseCclosure (global_State *g, CClosure *cl) {
+ int i;
+ for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
+ markvalue(g, &cl->upvalue[i]);
+ return sizeCclosure(cl->nupvalues);
+}
+
+static lu_mem traverseLclosure (global_State *g, LClosure *cl) {
+ int i;
+ markobject(g, cl->p); /* mark its prototype */
+ for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
+ markobject(g, cl->upvals[i]);
+ return sizeLclosure(cl->nupvalues);
+}
+
+
+static lu_mem traversestack (global_State *g, lua_State *th) {
+ int n = 0;
+ StkId o = th->stack;
+ if (o == NULL)
+ return 1; /* stack not completely built yet */
+ for (; o < th->top; o++) /* mark live elements in the stack */
+ markvalue(g, o);
+ if (g->gcstate == GCSatomic) { /* final traversal? */
+ StkId lim = th->stack + th->stacksize; /* real end of stack */
+ for (; o < lim; o++) /* clear not-marked stack slice */
+ setnilvalue(o);
+ }
+ else { /* count call infos to compute size */
+ CallInfo *ci;
+ for (ci = &th->base_ci; ci != th->ci; ci = ci->next)
+ n++;
+ }
+ return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
+ sizeof(CallInfo) * n;
+}
+
+
+/*
+** traverse one gray object, turning it to black (except for threads,
+** which are always gray).
+*/
+static void propagatemark (global_State *g) {
+ lu_mem size;
+ GCObject *o = g->gray;
+ lua_assert(isgray(o));
+ gray2black(o);
+ switch (gch(o)->tt) {
+ case LUA_TTABLE: {
+ Table *h = gco2t(o);
+ g->gray = h->gclist; /* remove from 'gray' list */
+ size = traversetable(g, h);
+ break;
+ }
+ case LUA_TLCL: {
+ LClosure *cl = gco2lcl(o);
+ g->gray = cl->gclist; /* remove from 'gray' list */
+ size = traverseLclosure(g, cl);
+ break;
+ }
+ case LUA_TCCL: {
+ CClosure *cl = gco2ccl(o);
+ g->gray = cl->gclist; /* remove from 'gray' list */
+ size = traverseCclosure(g, cl);
+ break;
+ }
+ case LUA_TTHREAD: {
+ lua_State *th = gco2th(o);
+ g->gray = th->gclist; /* remove from 'gray' list */
+ th->gclist = g->grayagain;
+ g->grayagain = o; /* insert into 'grayagain' list */
+ black2gray(o);
+ size = traversestack(g, th);
+ break;
+ }
+ case LUA_TPROTO: {
+ Proto *p = gco2p(o);
+ g->gray = p->gclist; /* remove from 'gray' list */
+ size = traverseproto(g, p);
+ break;
+ }
+ default: lua_assert(0); return;
+ }
+ g->GCmemtrav += size;
+}
+
+
+static void propagateall (global_State *g) {
+ while (g->gray) propagatemark(g);
+}
+
+
+static void propagatelist (global_State *g, GCObject *l) {
+ lua_assert(g->gray == NULL); /* no grays left */
+ g->gray = l;
+ propagateall(g); /* traverse all elements from 'l' */
+}
+
+/*
+** retraverse all gray lists. Because tables may be reinserted in other
+** lists when traversed, traverse the original lists to avoid traversing
+** twice the same table (which is not wrong, but inefficient)
+*/
+static void retraversegrays (global_State *g) {
+ GCObject *weak = g->weak; /* save original lists */
+ GCObject *grayagain = g->grayagain;
+ GCObject *ephemeron = g->ephemeron;
+ g->weak = g->grayagain = g->ephemeron = NULL;
+ propagateall(g); /* traverse main gray list */
+ propagatelist(g, grayagain);
+ propagatelist(g, weak);
+ propagatelist(g, ephemeron);
+}
+
+
+static void convergeephemerons (global_State *g) {
+ int changed;
+ do {
+ GCObject *w;
+ GCObject *next = g->ephemeron; /* get ephemeron list */
+ g->ephemeron = NULL; /* tables will return to this list when traversed */
+ changed = 0;
+ while ((w = next) != NULL) {
+ next = gco2t(w)->gclist;
+ if (traverseephemeron(g, gco2t(w))) { /* traverse marked some value? */
+ propagateall(g); /* propagate changes */
+ changed = 1; /* will have to revisit all ephemeron tables */
+ }
+ }
+ } while (changed);
+}
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** Sweep Functions
+** =======================================================
+*/
+
+
+/*
+** clear entries with unmarked keys from all weaktables in list 'l' up
+** to element 'f'
+*/
+static void clearkeys (global_State *g, GCObject *l, GCObject *f) {
+ for (; l != f; l = gco2t(l)->gclist) {
+ Table *h = gco2t(l);
+ Node *n, *limit = gnodelast(h);
+ for (n = gnode(h, 0); n < limit; n++) {
+ if (!ttisnil(gval(n)) && (iscleared(g, gkey(n)))) {
+ setnilvalue(gval(n)); /* remove value ... */
+ removeentry(n); /* and remove entry from table */
+ }
+ }
+ }
+}
+
+
+/*
+** clear entries with unmarked values from all weaktables in list 'l' up
+** to element 'f'
+*/
+static void clearvalues (global_State *g, GCObject *l, GCObject *f) {
+ for (; l != f; l = gco2t(l)->gclist) {
+ Table *h = gco2t(l);
+ Node *n, *limit = gnodelast(h);
+ int i;
+ for (i = 0; i < h->sizearray; i++) {
+ TValue *o = &h->array[i];
+ if (iscleared(g, o)) /* value was collected? */
+ setnilvalue(o); /* remove value */
+ }
+ for (n = gnode(h, 0); n < limit; n++) {
+ if (!ttisnil(gval(n)) && iscleared(g, gval(n))) {
+ setnilvalue(gval(n)); /* remove value ... */
+ removeentry(n); /* and remove entry from table */
+ }
+ }
+ }
+}
+
+
+static void freeobj (lua_State *L, GCObject *o) {
+ switch (gch(o)->tt) {
+ case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
+ case LUA_TLCL: {
+ luaM_freemem(L, o, sizeLclosure(gco2lcl(o)->nupvalues));
+ break;
+ }
+ case LUA_TCCL: {
+ luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues));
+ break;
+ }
+ case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
+ case LUA_TTABLE: luaH_free(L, gco2t(o)); break;
+ case LUA_TTHREAD: luaE_freethread(L, gco2th(o)); break;
+ case LUA_TUSERDATA: luaM_freemem(L, o, sizeudata(gco2u(o))); break;
+ case LUA_TSHRSTR:
+ G(L)->strt.nuse--;
+ /* go through */
+ case LUA_TLNGSTR: {
+ luaM_freemem(L, o, sizestring(gco2ts(o)));
+ break;
+ }
+ default: lua_assert(0);
+ }
+}
+
+
+#define sweepwholelist(L,p) sweeplist(L,p,MAX_LUMEM)
+static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count);
+
+
+/*
+** sweep the (open) upvalues of a thread and resize its stack and
+** list of call-info structures.
+*/
+static void sweepthread (lua_State *L, lua_State *L1) {
+ if (L1->stack == NULL) return; /* stack not completely built yet */
+ sweepwholelist(L, &L1->openupval); /* sweep open upvalues */
+ luaE_freeCI(L1); /* free extra CallInfo slots */
+ /* should not change the stack during an emergency gc cycle */
+ if (G(L)->gckind != KGC_EMERGENCY)
+ luaD_shrinkstack(L1);
+}
+
+
+/*
+** sweep at most 'count' elements from a list of GCObjects erasing dead
+** objects, where a dead (not alive) object is one marked with the "old"
+** (non current) white and not fixed.
+** In non-generational mode, change all non-dead objects back to white,
+** preparing for next collection cycle.
+** In generational mode, keep black objects black, and also mark them as
+** old; stop when hitting an old object, as all objects after that
+** one will be old too.
+** When object is a thread, sweep its list of open upvalues too.
+*/
+static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
+ global_State *g = G(L);
+ int ow = otherwhite(g);
+ int toclear, toset; /* bits to clear and to set in all live objects */
+ int tostop; /* stop sweep when this is true */
+ if (isgenerational(g)) { /* generational mode? */
+ toclear = ~0; /* clear nothing */
+ toset = bitmask(OLDBIT); /* set the old bit of all surviving objects */
+ tostop = bitmask(OLDBIT); /* do not sweep old generation */
+ }
+ else { /* normal mode */
+ toclear = maskcolors; /* clear all color bits + old bit */
+ toset = luaC_white(g); /* make object white */
+ tostop = 0; /* do not stop */
+ }
+ while (*p != NULL && count-- > 0) {
+ GCObject *curr = *p;
+ int marked = gch(curr)->marked;
+ if (isdeadm(ow, marked)) { /* is 'curr' dead? */
+ *p = gch(curr)->next; /* remove 'curr' from list */
+ freeobj(L, curr); /* erase 'curr' */
+ }
+ else {
+ if (testbits(marked, tostop))
+ return NULL; /* stop sweeping this list */
+ if (gch(curr)->tt == LUA_TTHREAD)
+ sweepthread(L, gco2th(curr)); /* sweep thread's upvalues */
+ /* update marks */
+ gch(curr)->marked = cast_byte((marked & toclear) | toset);
+ p = &gch(curr)->next; /* go to next element */
+ }
+ }
+ return (*p == NULL) ? NULL : p;
+}
+
+
+/*
+** sweep a list until a live object (or end of list)
+*/
+static GCObject **sweeptolive (lua_State *L, GCObject **p, int *n) {
+ GCObject ** old = p;
+ int i = 0;
+ do {
+ i++;
+ p = sweeplist(L, p, 1);
+ } while (p == old);
+ if (n) *n += i;
+ return p;
+}
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** Finalization
+** =======================================================
+*/
+
+static void checkSizes (lua_State *L) {
+ global_State *g = G(L);
+ if (g->gckind != KGC_EMERGENCY) { /* do not change sizes in emergency */
+ int hs = g->strt.size / 2; /* half the size of the string table */
+ if (g->strt.nuse < cast(lu_int32, hs)) /* using less than that half? */
+ luaS_resize(L, hs); /* halve its size */
+ luaZ_freebuffer(L, &g->buff); /* free concatenation buffer */
+ }
+}
+
+
+static GCObject *udata2finalize (global_State *g) {
+ GCObject *o = g->tobefnz; /* get first element */
+ lua_assert(isfinalized(o));
+ g->tobefnz = gch(o)->next; /* remove it from 'tobefnz' list */
+ gch(o)->next = g->allgc; /* return it to 'allgc' list */
+ g->allgc = o;
+ resetbit(gch(o)->marked, SEPARATED); /* mark that it is not in 'tobefnz' */
+ lua_assert(!isold(o)); /* see MOVE OLD rule */
+ if (!keepinvariantout(g)) /* not keeping invariant? */
+ makewhite(g, o); /* "sweep" object */
+ return o;
+}
+
+
+static void dothecall (lua_State *L, void *ud) {
+ UNUSED(ud);
+ luaD_call(L, L->top - 2, 0, 0);
+}
+
+
+static void GCTM (lua_State *L, int propagateerrors) {
+ global_State *g = G(L);
+ const TValue *tm;
+ TValue v;
+ setgcovalue(L, &v, udata2finalize(g));
+ tm = luaT_gettmbyobj(L, &v, TM_GC);
+ if (tm != NULL && ttisfunction(tm)) { /* is there a finalizer? */
+ int status;
+ lu_byte oldah = L->allowhook;
+ int running = g->gcrunning;
+ L->allowhook = 0; /* stop debug hooks during GC metamethod */
+ g->gcrunning = 0; /* avoid GC steps */
+ setobj2s(L, L->top, tm); /* push finalizer... */
+ setobj2s(L, L->top + 1, &v); /* ... and its argument */
+ L->top += 2; /* and (next line) call the finalizer */
+ status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
+ L->allowhook = oldah; /* restore hooks */
+ g->gcrunning = (lu_byte)running; /* restore state */
+ if (status != LUA_OK && propagateerrors) { /* error while running __gc? */
+ if (status == LUA_ERRRUN) { /* is there an error object? */
+ const char *msg = (ttisstring(L->top - 1))
+ ? svalue(L->top - 1)
+ : "no message";
+ luaO_pushfstring(L, "error in __gc metamethod (%s)", msg);
+ status = LUA_ERRGCMM; /* error in __gc metamethod */
+ }
+ luaD_throw(L, status); /* re-throw error */
+ }
+ }
+}
+
+
+/*
+** move all unreachable objects (or 'all' objects) that need
+** finalization from list 'finobj' to list 'tobefnz' (to be finalized)
+*/
+static void separatetobefnz (lua_State *L, int all) {
+ global_State *g = G(L);
+ GCObject **p = &g->finobj;
+ GCObject *curr;
+ GCObject **lastnext = &g->tobefnz;
+ /* find last 'next' field in 'tobefnz' list (to add elements in its end) */
+ while (*lastnext != NULL)
+ lastnext = &gch(*lastnext)->next;
+ while ((curr = *p) != NULL) { /* traverse all finalizable objects */
+ lua_assert(!isfinalized(curr));
+ lua_assert(testbit(gch(curr)->marked, SEPARATED));
+ if (!(iswhite(curr) || all)) /* not being collected? */
+ p = &gch(curr)->next; /* don't bother with it */
+ else {
+ l_setbit(gch(curr)->marked, FINALIZEDBIT); /* won't be finalized again */
+ *p = gch(curr)->next; /* remove 'curr' from 'finobj' list */
+ gch(curr)->next = *lastnext; /* link at the end of 'tobefnz' list */
+ *lastnext = curr;
+ lastnext = &gch(curr)->next;
+ }
+ }
+}
+
+
+/*
+** if object 'o' has a finalizer, remove it from 'allgc' list (must
+** search the list to find it) and link it in 'finobj' list.
+*/
+void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
+ global_State *g = G(L);
+ if (testbit(gch(o)->marked, SEPARATED) || /* obj. is already separated... */
+ isfinalized(o) || /* ... or is finalized... */
+ gfasttm(g, mt, TM_GC) == NULL) /* or has no finalizer? */
+ return; /* nothing to be done */
+ else { /* move 'o' to 'finobj' list */
+ GCObject **p;
+ GCheader *ho = gch(o);
+ if (g->sweepgc == &ho->next) { /* avoid removing current sweep object */
+ lua_assert(issweepphase(g));
+ g->sweepgc = sweeptolive(L, g->sweepgc, NULL);
+ }
+ /* search for pointer pointing to 'o' */
+ for (p = &g->allgc; *p != o; p = &gch(*p)->next) { /* empty */ }
+ *p = ho->next; /* remove 'o' from root list */
+ ho->next = g->finobj; /* link it in list 'finobj' */
+ g->finobj = o;
+ l_setbit(ho->marked, SEPARATED); /* mark it as such */
+ if (!keepinvariantout(g)) /* not keeping invariant? */
+ makewhite(g, o); /* "sweep" object */
+ else
+ resetoldbit(o); /* see MOVE OLD rule */
+ }
+}
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** GC control
+** =======================================================
+*/
+
+
+/*
+** set a reasonable "time" to wait before starting a new GC cycle;
+** cycle will start when memory use hits threshold
+*/
+static void setpause (global_State *g, l_mem estimate) {
+ l_mem debt, threshold;
+ estimate = estimate / PAUSEADJ; /* adjust 'estimate' */
+ threshold = (g->gcpause < MAX_LMEM / estimate) /* overflow? */
+ ? estimate * g->gcpause /* no overflow */
+ : MAX_LMEM; /* overflow; truncate to maximum */
+ debt = -cast(l_mem, threshold - gettotalbytes(g));
+ luaE_setdebt(g, debt);
+}
+
+
+#define sweepphases \
+ (bitmask(GCSsweepstring) | bitmask(GCSsweepudata) | bitmask(GCSsweep))
+
+
+/*
+** enter first sweep phase (strings) and prepare pointers for other
+** sweep phases. The calls to 'sweeptolive' make pointers point to an
+** object inside the list (instead of to the header), so that the real
+** sweep do not need to skip objects created between "now" and the start
+** of the real sweep.
+** Returns how many objects it swept.
+*/
+static int entersweep (lua_State *L) {
+ global_State *g = G(L);
+ int n = 0;
+ g->gcstate = GCSsweepstring;
+ lua_assert(g->sweepgc == NULL && g->sweepfin == NULL);
+ /* prepare to sweep strings, finalizable objects, and regular objects */
+ g->sweepstrgc = 0;
+ g->sweepfin = sweeptolive(L, &g->finobj, &n);
+ g->sweepgc = sweeptolive(L, &g->allgc, &n);
+ return n;
+}
+
+
+/*
+** change GC mode
+*/
+void luaC_changemode (lua_State *L, int mode) {
+ global_State *g = G(L);
+ if (mode == g->gckind) return; /* nothing to change */
+ if (mode == KGC_GEN) { /* change to generational mode */
+ /* make sure gray lists are consistent */
+ luaC_runtilstate(L, bitmask(GCSpropagate));
+ g->GCestimate = gettotalbytes(g);
+ g->gckind = KGC_GEN;
+ }
+ else { /* change to incremental mode */
+ /* sweep all objects to turn them back to white
+ (as white has not changed, nothing extra will be collected) */
+ g->gckind = KGC_NORMAL;
+ entersweep(L);
+ luaC_runtilstate(L, ~sweepphases);
+ }
+}
+
+
+/*
+** call all pending finalizers
+*/
+static void callallpendingfinalizers (lua_State *L, int propagateerrors) {
+ global_State *g = G(L);
+ while (g->tobefnz) {
+ resetoldbit(g->tobefnz);
+ GCTM(L, propagateerrors);
+ }
+}
+
+
+void luaC_freeallobjects (lua_State *L) {
+ global_State *g = G(L);
+ int i;
+ separatetobefnz(L, 1); /* separate all objects with finalizers */
+ lua_assert(g->finobj == NULL);
+ callallpendingfinalizers(L, 0);
+ g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */
+ g->gckind = KGC_NORMAL;
+ sweepwholelist(L, &g->finobj); /* finalizers can create objs. in 'finobj' */
+ sweepwholelist(L, &g->allgc);
+ for (i = 0; i < g->strt.size; i++) /* free all string lists */
+ sweepwholelist(L, &g->strt.hash[i]);
+ lua_assert(g->strt.nuse == 0);
+}
+
+
+static l_mem atomic (lua_State *L) {
+ global_State *g = G(L);
+ l_mem work = -cast(l_mem, g->GCmemtrav); /* start counting work */
+ GCObject *origweak, *origall;
+ lua_assert(!iswhite(obj2gco(g->mainthread)));
+ markobject(g, L); /* mark running thread */
+ /* registry and global metatables may be changed by API */
+ markvalue(g, &g->l_registry);
+ markmt(g); /* mark basic metatables */
+ /* remark occasional upvalues of (maybe) dead threads */
+ remarkupvals(g);
+ propagateall(g); /* propagate changes */
+ work += g->GCmemtrav; /* stop counting (do not (re)count grays) */
+ /* traverse objects caught by write barrier and by 'remarkupvals' */
+ retraversegrays(g);
+ work -= g->GCmemtrav; /* restart counting */
+ convergeephemerons(g);
+ /* at this point, all strongly accessible objects are marked. */
+ /* clear values from weak tables, before checking finalizers */
+ clearvalues(g, g->weak, NULL);
+ clearvalues(g, g->allweak, NULL);
+ origweak = g->weak; origall = g->allweak;
+ work += g->GCmemtrav; /* stop counting (objects being finalized) */
+ separatetobefnz(L, 0); /* separate objects to be finalized */
+ markbeingfnz(g); /* mark objects that will be finalized */
+ propagateall(g); /* remark, to propagate `preserveness' */
+ work -= g->GCmemtrav; /* restart counting */
+ convergeephemerons(g);
+ /* at this point, all resurrected objects are marked. */
+ /* remove dead objects from weak tables */
+ clearkeys(g, g->ephemeron, NULL); /* clear keys from all ephemeron tables */
+ clearkeys(g, g->allweak, NULL); /* clear keys from all allweak tables */
+ /* clear values from resurrected weak tables */
+ clearvalues(g, g->weak, origweak);
+ clearvalues(g, g->allweak, origall);
+ g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */
+ work += g->GCmemtrav; /* complete counting */
+ return work; /* estimate of memory marked by 'atomic' */
+}
+
+
+static lu_mem singlestep (lua_State *L) {
+ global_State *g = G(L);
+ switch (g->gcstate) {
+ case GCSpause: {
+ /* start to count memory traversed */
+ g->GCmemtrav = g->strt.size * sizeof(GCObject*);
+ lua_assert(!isgenerational(g));
+ restartcollection(g);
+ g->gcstate = GCSpropagate;
+ return g->GCmemtrav;
+ }
+ case GCSpropagate: {
+ if (g->gray) {
+ lu_mem oldtrav = g->GCmemtrav;
+ propagatemark(g);
+ return g->GCmemtrav - oldtrav; /* memory traversed in this step */
+ }
+ else { /* no more `gray' objects */
+ lu_mem work;
+ int sw;
+ g->gcstate = GCSatomic; /* finish mark phase */
+ g->GCestimate = g->GCmemtrav; /* save what was counted */;
+ work = atomic(L); /* add what was traversed by 'atomic' */
+ g->GCestimate += work; /* estimate of total memory traversed */
+ sw = entersweep(L);
+ return work + sw * GCSWEEPCOST;
+ }
+ }
+ case GCSsweepstring: {
+ int i;
+ for (i = 0; i < GCSWEEPMAX && g->sweepstrgc + i < g->strt.size; i++)
+ sweepwholelist(L, &g->strt.hash[g->sweepstrgc + i]);
+ g->sweepstrgc += i;
+ if (g->sweepstrgc >= g->strt.size) /* no more strings to sweep? */
+ g->gcstate = GCSsweepudata;
+ return i * GCSWEEPCOST;
+ }
+ case GCSsweepudata: {
+ if (g->sweepfin) {
+ g->sweepfin = sweeplist(L, g->sweepfin, GCSWEEPMAX);
+ return GCSWEEPMAX*GCSWEEPCOST;
+ }
+ else {
+ g->gcstate = GCSsweep;
+ return 0;
+ }
+ }
+ case GCSsweep: {
+ if (g->sweepgc) {
+ g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
+ return GCSWEEPMAX*GCSWEEPCOST;
+ }
+ else {
+ /* sweep main thread */
+ GCObject *mt = obj2gco(g->mainthread);
+ sweeplist(L, &mt, 1);
+ checkSizes(L);
+ g->gcstate = GCSpause; /* finish collection */
+ return GCSWEEPCOST;
+ }
+ }
+ default: lua_assert(0); return 0;
+ }
+}
+
+
+/*
+** advances the garbage collector until it reaches a state allowed
+** by 'statemask'
+*/
+void luaC_runtilstate (lua_State *L, int statesmask) {
+ global_State *g = G(L);
+ while (!testbit(statesmask, g->gcstate))
+ singlestep(L);
+}
+
+
+static void generationalcollection (lua_State *L) {
+ global_State *g = G(L);
+ lua_assert(g->gcstate == GCSpropagate);
+ if (g->GCestimate == 0) { /* signal for another major collection? */
+ luaC_fullgc(L, 0); /* perform a full regular collection */
+ g->GCestimate = gettotalbytes(g); /* update control */
+ }
+ else {
+ lu_mem estimate = g->GCestimate;
+ luaC_runtilstate(L, bitmask(GCSpause)); /* run complete (minor) cycle */
+ g->gcstate = GCSpropagate; /* skip restart */
+ if (gettotalbytes(g) > (estimate / 100) * g->gcmajorinc)
+ g->GCestimate = 0; /* signal for a major collection */
+ else
+ g->GCestimate = estimate; /* keep estimate from last major coll. */
+
+ }
+ setpause(g, gettotalbytes(g));
+ lua_assert(g->gcstate == GCSpropagate);
+}
+
+
+static void incstep (lua_State *L) {
+ global_State *g = G(L);
+ l_mem debt = g->GCdebt;
+ int stepmul = g->gcstepmul;
+ if (stepmul < 40) stepmul = 40; /* avoid ridiculous low values (and 0) */
+ /* convert debt from Kb to 'work units' (avoid zero debt and overflows) */
+ debt = (debt / STEPMULADJ) + 1;
+ debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM;
+ do { /* always perform at least one single step */
+ lu_mem work = singlestep(L); /* do some work */
+ debt -= work;
+ } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause);
+ if (g->gcstate == GCSpause)
+ setpause(g, g->GCestimate); /* pause until next cycle */
+ else {
+ debt = (debt / stepmul) * STEPMULADJ; /* convert 'work units' to Kb */
+ luaE_setdebt(g, debt);
+ }
+}
+
+
+/*
+** performs a basic GC step
+*/
+void luaC_forcestep (lua_State *L) {
+ global_State *g = G(L);
+ int i;
+ if (isgenerational(g)) generationalcollection(L);
+ else incstep(L);
+ /* run a few finalizers (or all of them at the end of a collect cycle) */
+ for (i = 0; g->tobefnz && (i < GCFINALIZENUM || g->gcstate == GCSpause); i++)
+ GCTM(L, 1); /* call one finalizer */
+}
+
+
+/*
+** performs a basic GC step only if collector is running
+*/
+void luaC_step (lua_State *L) {
+ global_State *g = G(L);
+ if (g->gcrunning) luaC_forcestep(L);
+ else luaE_setdebt(g, -GCSTEPSIZE); /* avoid being called too often */
+}
+
+
+
+/*
+** performs a full GC cycle; if "isemergency", does not call
+** finalizers (which could change stack positions)
+*/
+void luaC_fullgc (lua_State *L, int isemergency) {
+ global_State *g = G(L);
+ int origkind = g->gckind;
+ lua_assert(origkind != KGC_EMERGENCY);
+ if (isemergency) /* do not run finalizers during emergency GC */
+ g->gckind = KGC_EMERGENCY;
+ else {
+ g->gckind = KGC_NORMAL;
+ callallpendingfinalizers(L, 1);
+ }
+ if (keepinvariant(g)) { /* may there be some black objects? */
+ /* must sweep all objects to turn them back to white
+ (as white has not changed, nothing will be collected) */
+ entersweep(L);
+ }
+ /* finish any pending sweep phase to start a new cycle */
+ luaC_runtilstate(L, bitmask(GCSpause));
+ luaC_runtilstate(L, ~bitmask(GCSpause)); /* start new collection */
+ luaC_runtilstate(L, bitmask(GCSpause)); /* run entire collection */
+ if (origkind == KGC_GEN) { /* generational mode? */
+ /* generational mode must be kept in propagate phase */
+ luaC_runtilstate(L, bitmask(GCSpropagate));
+ }
+ g->gckind = (lu_byte)origkind;
+ setpause(g, gettotalbytes(g));
+ if (!isemergency) /* do not run finalizers during emergency GC */
+ callallpendingfinalizers(L, 1);
+}
+
+/* }====================================================== */
+
+
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